NASA's DC-8 is prepared for an early morning evaluation flight of the Methane Sounder Instrument on August 24, 2011. (NSERC/Emily Schaller)› View Larger Image

Methane Sounder Instrument principal investigator Haris Riris (left) and Stewart Wu (right) test the alignment of the laser underneath the DC-8 at the NASA Dryden Aircraft Operations Facility. (NSERC/Emily Schaller) › View Larger Image NASA's DC-8 flew three flights over the Central Valley of California during August to test the performance of a laser-based instrument designed to measure methane in Earth's atmosphere. The Methane Sounder Instrument, built by principal investigator Haris Riris and his team from NASA's Goddard Space Flight Center, may one day map methane from a future Earth or Mars-orbiting satellite.

On Earth, methane is an important greenhouse gas produced by certain types of bacteria in soils and in the digestive tracts of some animals. Large quantities of methane are also produced as a result of forest fires and human industrial processes. Knowledge of the global distribution and abundance of methane is important for understanding global climate change.

Before instruments are installed on a satellite or spacecraft, many are first tested aboard NASA airplanes. The Methane Sounder Instrument team spent two weeks at NASA's Dryden Aircraft Operations Facility in Palmdale, Calif., installing and testing their instrument on the DC-8. The team spent several days aligning and testing the instrument on the ground before testing its performance on flights over the California Central Valley.

The Methane Sounder Instrument detects methane using an infrared laser beam. As the laser passes through the atmosphere and bounces off the ground, methane molecules in the atmosphere absorb some of the light from the laser. Measuring the amount of absorption that occurs as the instrument passes over different locations allows the team to build methane maps.

NASA's DC-8 flies over California's San Joaquin Valley during evaluation of a methane sounder instrument. (NSERC/Emily Schaller) › View Larger Image Although current Earth-orbiting satellites have instruments that can detect and map Earth's methane, the laser-based system of the Methane Sounder will enable greater accuracy in methane detections and higher-resolution methane maps than are possible with current non-laser-based instruments. With some modifications, the laser system could also be used for a Mars-orbiting satellite.

The instrument performed well and detected the presence of methane in the atmosphere as the aircraft flew a variety of altitudes over the San Joaquin Valley Aug. 23-25.

"The Methane Sounder is the first demonstration of methane detection using lasers from an aircraft flying above 30,000 feet," said Riris. "The sensor should be a valuable tool for monitoring greenhouse gas emissions, especially in the Arctic." Funding for the Methane Sounder was provided by NASA's Astrobiology Science and Technology Instrument Development program with support from the ASCENDS CO2 Instrument Incubator Program.